Recently, interests in an aerogel having excellent insulation properties have grown as industrial technologies are modernized. Aerogels developed to date may include an organic aerogel, such as resorcinol-formaldehyde or melamine-formaldehyde aerogel particles, and an inorganic aerogel including metal oxide such as a silica (SiO2), alumina (Al2O3), titania (TiO2), or carbon (C) aerogel.
Among these aerogels, the silica aerogel is a highly porous material, wherein since the silica aerogel has high porosity and specific surface area as well as low thermal conductivity, applications in various areas, such as heat insulation materials, catalysts, sound-absorbing materials, and interlayer dielectric materials of a semiconductor circuit, are expected. Although commercialization rate is very low due to complex manufacturing processes and low mechanical strength, early application products have been released as a result of continuous research, and the expansion of the market including the heat insulation materials is increasingly faster.
Since the silica aerogel has low mechanical strength due to its porous structure, the silica aerogel is normally commercialized in a form, such as an aerogel blanket or aerogel sheet, by compositing with a base material such as glass fibers, ceramic fibers, or polymer fibers.
For example, with respect to a silica aerogel-containing blanket using the silica aerogel, it is prepared by the steps of silica sol preparation, gelation, aging, and surface modification. However, with respect to the typical method of preparing a silica aerogel-containing blanket as described above, the process is complex and is uneconomical in terms of time and cost. Also, the surface modification step of the silica aerogel is essential, and a large amount of organic solvent and an expensive hydrophobic agent are used for this purpose. In addition, since recovery and separation processes of by-products generated in the surface modification step are essential, there are a lot of difficulties in the commercialization of the silica aerogel-containing blanket.
Furthermore, alkoxide or water glass is mainly used as a silica precursor during the preparation of the silica aerogel blanket. However, since the alkoxide is more expensive than the water glass, economic efficiency may be low. Also, the water glass may be less expensive and safer than the alkoxide, but, since a step of solvent substitution to an organic solvent is essentially required, processing time may be increased, an excessive amount of wastewater may be generated, and an expensive surface modifier may be used in the surface modification step.
With respect to aerogel powder, manufacturing techniques, such as a simultaneous substitution method and a co-precursor method, for omitting the solvent substitution step or reducing an amount of the used surface modifier have been developed, but, with respect to the blanket, since solvent diffusion in the gel is not easy in comparison to the aerogel powder, the above processes are not easy to be used.
Therefore, there is a need to develop a method which may omit the surface modification step or may reduce the amount of the used surface modifier during the preparation of the blanket using the silica aerogel.